What is Kurp? : Curves are the curved parts of the road, combining the correct paths in different directions. When the Aliyman road intersects with a second aliyman, it can only pass through the roads called curves because it cannot pass through this angular section. Since the most uniform curve will be the spring of a circle, the curves on the rail are the arc of a circle with a certain radius. Curves are divided into two groups of horizontal curves and vertical curves.